MIl-PRF-13830 and Inspection of Mirrors

[Delta]

Hi folks.

Not expecting much of a response (specialist area) but I'll try.

Does anyone know how to inspect mirrors for cosmetic defects??

The HMD project I'm working involves CRT driven combiners, and from that I've become well acquainted with MIL-PRF-13830 on display eyepieces. A colleague is asking about an associated product which instead projects the images on to a display visor, and how the mirror that projects the image can be assessed most appropriately.

Since 1997, all the Military Standards for optical assemblies seem to be rolled into MIL-PRF-13830, which I see as more of a standard for transparent assemblies, combiners, etc. Further, although mirrors are addressed in Appendix B, the only inspection options it gives is rear illuminating the item (i.e. in tranmission), or from above (inspection from scattered light).

There appears to be nothing to show how a mirror should be validated for acceptance.

Anyone out there in the aerospace industry that specialises in mirrors? How do you assess your product for quality?

Many thanks in advance.

 

[FredGarvin]

I have no experience in this area, so I'll probably ask more questions than anything else. I just took a brief read through of MIL-PRF-13830B. There's 82 pages of fun. Looking at chapter 4, section 4.2 it appears to show a pretty good description of tests. You're saying that you don't think that mirrors fall under this section's control?

If all else fails, I would first try contacting NASA's space optics facility:
http://optics.nasa.gov/

I have done this many times and had great success with other NASA installations and sharing of test set ups, etc...I think it would be time well spent to try giving them a call.

You might also try the Society of Photo-Optical Instrumentation Engineers:
http://spie.org/

As an aside, here is a pretty cool picture of an inspection of the Hubble primary mirror:
http://mix.msfc.nasa.gov/IMAGES/MEDIUM/8218871.jpg

 

[ravenprp]

Hi there,

I am not a specialist in this area, but I did some research on MIL-PRF-13830 and inspection of mirrors. From my understanding, MIL-PRF-13830 is a standard for transparent assemblies, but it also includes guidelines for inspection of mirrors in Appendix B.

According to Appendix B, there are two methods for inspecting mirrors: rear illumination and scattered light. Rear illumination involves passing light through the mirror and observing the reflected image for any defects. Scattered light involves shining a light on the mirror at an angle and observing the reflected light for any defects.

In terms of acceptance criteria, it seems that MIL-PRF-13830 does not provide specific guidelines for mirrors. Instead, it states that the acceptance criteria should be determined by the procuring activity. This means that the specific requirements for your project may be determined by your colleague or the organization you are working with.

In addition to MIL-PRF-13830, there are other standards and guidelines that may be useful for inspecting mirrors. For example, ASTM E903 provides a test method for measuring specular gloss, which can be used to assess the surface quality of a mirror.

I hope this information is helpful and I wish you the best in finding a suitable method for inspecting mirrors for your project.